Carrageenan-grafted magnetite nanoparticles as recyclable sorbents for dye removal

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2015-07, Vol.17 (7), p.1-15, Article 302
• Main Authors: Daniel-da-Silva, Ana L., Salgueiro, Ana M., Creaney, Bianca, Oliveira-Silva, Rui, Silva, Nuno J. O., Trindade, Tito
• Format: Article
• Language: English
• Subjects: Adsorption; Characterization and Evaluation of Materials; Chemistry and Materials Science; Color removal; Decontamination; Dyes; Infrared spectroscopy; Inorganic Chemistry; Iron oxides; Isotherms; Kinetics; Lasers; Magnetite; Materials Science; Mathematical models; Nanoparticles; Nanotechnology; Optical Devices; Optics; Photonics; Physical Chemistry; Research Paper; Saccharides; Silica; Sorbents; Surface chemistry
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-015-3108-0

The efforts dedicated to improving water decontamination procedures have prompted the interest in the development of efficient, inexpensive, and reusable sorbents for the uptake of dye pollutants. In this work, novel sorbents consisting of carrageenan polysaccharides grafted to magnetic iron oxide nanoparticles were prepared. κ- and ι-carrageenan were first chemically modified by carboxymethylation and then covalently attached via amide bond to the surface of aminated silica-coated magnetite nanoparticles, both steps monitored using infrared spectroscopy (FTIR) analysis. The kinetics and the equilibrium behavior of the cationic dye methylene blue (MB) adsorption onto the carrageenan sorbents were investigated. ι-carrageenan sorbents displayed higher MB adsorption capacity that was ascribed to high content of sulfonate groups. Overall, the pseudo-second order equation provided a good description of the adsorption kinetics. The κ-carrageenan sorbents followed an unusual Z-type equilibrium adsorption isotherm whereas the isotherm of ι-carrageenan sorbents, although displaying a conventional shape, could not be successfully predicted by isotherm models commonly used. Noteworthy, both sorbents were long-term stable and could easily be recycled by simply rinsing with KCl aqueous solution. The removal efficiency of κ-carrageenan sorbents was 92 % in the first adsorption cycle and kept high (>80 %) even after six consecutive adsorption/desorption cycles.